Feature: Interactive local GitLab CI setup script

While working on CI changes (especially adding and testing new jobs like the LibreSSL ones), I needed a quick way to run only selected pipelines locally and to validate new CI jobs before pushing.

This script is what I’ve been using for that. It simply reads the existing .gitlab-ci.yml, lists all jobs, and lets you run any one of them (or the full set) locally via gitlab-ci-local. If someone adds a new CI job to the YAML, it automatically shows up in the menu and can be tested the same way.

I found this very useful while iterating on CI and debugging failures, and I think it could be helpful for other contributors as well, so I’m proposing it as an optional developer helper.

Closes #348 (closed)